The n-type Si-based materials applied on the front surface of IBC-SHJ solar cells

Interdigitated back contact silicon hetero-junction(IBC-SHJ) solar cells exhibit excellent performance owing to the IBC and SHJ structures.The front surface field(FSF) layer composed of electric field passivation and chemical passivation has been proved to play an important role in IBC-SHJ solar cells.The electric field passivated layer n^+-a-Si: H, an n-type Si alloy with carbon or oxygen in amorphous phase, is simulated in this study to investigate its effect on IBC-SHJ.It is indicated that the n^+-a-Si: H layer with wider band gap can reduce the light absorption on the front side efficaciously,which hinders the surface recombination of photo-generated carriers and thus contributes to the improvement of the short circuit current density Jsc.The highly doped n^+-a-Si: H can result in the remakable energy band bending, which makes it outstanding in the field passivation, while it makes little contribution to the chemical passivation.It is noteworthy that when the electric field intensity exceeds 1.3 × 10^5 V/cm, the efficiency decrease caused by the inferior chemical passivation is only 0.16%.In this study, the IBC-SHJ solar cell with a front n^+-a-Si: H field passivation layer is simulated, which shows the high efficiency of 26% in spite of the inferior chemical passivation on the front surface.

Sub-stochiometric MoO_(x) by radio-frequency magnetron sputtering as hole-selective passivating contacts for silicon heterojunction solar cells

The silicon heterojunction(SHJ)solar cell has long been considered as one of the most promising candidates for the next-generation PV market.Transition metal oxides(TMOs)show good carrier selectivity when combined with c-Si solar cells.This has led to the rapid demonstration of the remarkable potential of TMOs(especially MoO_(x))with high work function to replace the p-type a-Si:H emitting layer.MoO_(x) can induce a strong inversion layer on the interface of n-type c-Si,which is beneficial to the extraction and conduction of holes.In this paper,the radio-frequency(RF)magnetron sputtering is used to deposit MoO_(x) films.The optical,electrical and structural properties of MoO_(x) films are measured and analyzed,with focus on the inherent compositions and work function.Then the MoO_(x) films are applied into SHJ solar cells.When the MoO_(x) works as a buffer layer between ITO/p-a-Si:H interface in the reference SHJ solar cell,a conversion efficiency of 19.1%can be obtained.When the MoOx is used as a hole transport layer(HTL),the device indicates a desirable conversion efficiency of 17.5%.To the best of our knowledge,this current efficiency is the highest one for the MoO_(x) film as HTL by RF sputtering.

硼掺杂对用于SHJ太阳电池的nc-Si∶H薄膜微结构的影响

采用RF-PECVD法在低温低功率密度下制备了p型nc-Si∶H薄膜,并系统地研究了硼掺杂对薄膜微结构及光电性能的影响。结果表明:由于"硼掺杂效应",随着掺硼比的增大,nc-Si∶H薄膜的晶化率逐渐降低,晶粒尺寸减小,薄膜的择优取向由[111]变为[220];光学带隙逐渐减小,电导率则先升后降;本实验中薄膜的最优掺杂比为0.3%。以优化后的p型nc-Si∶H薄膜做窗口层,SHJ太阳电池的性能得到明显改善,获得了效率为14.1%的电池。

SHJ太阳电池叠层减反结构及光电性能研究

创新性提出低温退火下异质结(SHJ)太阳电池的叠层减反射结构。采用等离子体增强化学气相沉积技术在沉积金属电极后的SHJ太阳电池入光面依次沉积SiN_x和SiO_x薄膜,形成SiO_x/SiN_x/IWO三层减反射膜,则电极部分为SiO_x/SiN_x/Ag/IWO的叠层结构,经低温退火银浆穿透表面介电薄膜形成导电通路。结果表明,SiO_x/SiN_x/IWO叠层具有优异的光学透过性,并显著降低电池表面反射损失。与单层IWO薄膜相比,厚度分别为90、30、60 nm的SiO_x/SiN_x/IWO的三层减反射膜使平均反射率下降至5.9%,对应波段外量子效率显著提高,SHJ电池短路电流密度和转换效率分别提高1.22 mA/cm^2和0.96%,具有巨大的应用潜力。

High-quality industrial n-type silicon wafers with an efficiency of over 23% for Si heterojunction solar cells

n-type CZ-Si wafers featuring longer minority carrier lifetime and higher tolerance of certain metal contamination can offer one of the best Si-based solar cells. In this study, Si heterojuction （SHJ） solar cells which was fabricated with different wafers in the top, middle and tail positions of the ingot, exhibited a stable high efficiency of〉 22% in spite of the various profiles of the resistivity and lifetime, which demonstrated the high material utilization of n-type ingot. In addition, for effectively converting the sunlight into electrical power, the pyramid size, pyramid density and roughness of surface of the Cz-Si wafer were investigated by scanning electron microscope （SEM） and transmission electron microscope （TEM）. Furthermore, the dependence of SHJ solar cell open- circuit voltage on the surface topography was discussed, which indicated that the uniformity of surface pyramid helps to improve the open-circuit voltage and conversion efficiency. Moreover, the simulation revealed that the highest efficiency of the SHJ solar cell could be achieved by the wafer with a thickness of 100 μm. Fortunately, over 23% of the conversion efficiency of the SHJ solar cell with a wafer thickness of 100 μm was obtained based on the systematic optimization of cell fabrication process in the pilot production line. Evidently, the large availability of both n-type ingot and thinner wafer strongly supported the lower cost fabrication of high efficiency SHJ solar cell.

硅基异质结太阳电池新进展

非晶硅/晶体硅异质结太阳电池(SHJ)是在晶体硅上沉积非晶硅薄膜,它综合了晶体硅电池与薄膜电池的优势,具有结构简单、工艺温度低、钝化效果好、开路电压高、温度特性好、双面发电等优点,是高转换效率硅基太阳电池的热点方向之一。本文首先综述了近几年SHJ电池制造工艺技术的进步,包括臭氧清洗硅片、热丝化学气相沉积技术沉积非晶硅薄膜、透明导电薄膜沉积方法和材料的改进,以及新型金属化电极技术在SHJ电池中的应用所取得的进展。然后介绍了结合背面结技术、载流子选择性钝化接触技术的硅异质结电池以及薄型硅异质结太阳电池最新研究情况。进一步分析了与叉指式背接触技术相结合的硅异质结电池、与钙钛矿太阳电池技术相结合的钙钛矿/硅异质结两端叠层太阳电池的研究现状,指出硅基异质结太阳电池是迈向更高效率太阳电池的基石。

非晶硅对MoO_x/c-Si异质结太阳电池器件的影响

室温下电子束蒸发沉积氧化钼（MoOx）薄膜呈非晶态,光学带隙约为3.6 eV,与单晶硅表面构成MoOx/c-Si异质结并具有钝化作用,但明显低于i∶α-Si∶H钝化。ITO/MoOx/i∶α-Si∶H/n∶c-Si/i∶α-Si∶H/n＋∶α-Si∶H/Al太阳电池结构,既有晶硅前后表面钝化,又增加了背电场层,适当的MoOx厚度可获得电池的最高效率（15.5%）;若取消晶硅表面i∶a-Si∶H钝化,与HIT（heterojunction with intrinsic thinlayer）电池类似,硅的前表面复合增大,电池效率降为11.5%;若取消背表面i∶a-Si∶H钝化及背电场材料n＋∶a-Si∶H,电池效率急剧下降到8.3%,这表明背表面钝化及背电场,对MoOx/c-Si异质结太阳电池特性具有更为重要的作用,对高效器件制备具有一定指导意义。